1. Field of the Invention
This invention relates to improvements in systems for spraying a powder circumferentially around a pipe or the like. More particularly, this invention involved a suction return to prevent contamination of the air in the region of the pipe joint and to reduce the loss of powder from the system.
2. Description of the Prior Art
In my prior co-pending application, referred to above, there is described a system for spraying or dispensing a powdered material circumferentially around a pipe. The pipe itself is made up from pipe sections which have been previously coated at the mill except for the ends thereof which are left uncoated so that the sections can be welded together in the field in end-to-end relation. The apparatus of the aforementioned co-pending application, therefore, deposits powder on the weld joints (which have been previously heated) to complete the coating of the pipe. However, it is difficult to meter exactly the quantity of powder to be supplied to each weld joint. Obviously, an insufficient quantity will result in a poor or inadequate coating of the weld joint. In practice, a quantity of powder slightly in excess of that required is supplied to the weld joint. This excess powder can result in a contamination of the air in the area of the pipe joint, and it can also result in a loss of powder from the system.